Using webcams for Astrophotography in Linux

Update 10/01/2017

With the release of the Raspberry pi and its camera, this project was abandoned. Quite frankly the Pi camera offers us RAW output, higher resolution that the below webcams, and the option to purchase a camera without an IR filter attached!

A far better base to start from then the below webcams, which now is only here for historic purposes.

Indeed I have started to do that already. No project page on my site as of yet, but you can find the github project page here for now:

github.com/ZivaVatra/raspberrypi-astro-capture

Archived information follows

I love space, always had. I always wanted to take photos of it. So recently I've been attempting to get into astrophotography. So far I've been trying to do so using a DSLR and Zoom lens. This is good, but I believe it can be done better. The DSLR is very good, but there are some tricks I would like to try:

These two things are problematic to do. Firstly, every consumer infrared camera has to have an Infrared blocking filter. This is due to the fact (allegedly discovered in Japan sometime after CCD cameras became available to the public) that certain clothing is completely transparent to IR. Much perving ensued..... and now not only are IR filters mandatory on cameras, they are usually very hard (if not impossible) to remove without damaging the CCD.

The Bayer filter is even harder to remove. That is usually a very fine filter matrix installed just a few microns from the CCD itself. Removing it has been reported to have been done by some people (usually on high end DSLR's), but it is difficult and risky.

Neither of the above are something I want to do to my DSLR, If I break it I will not be able to afford another one! As such I've been thinking of using cheap webcams for this. Yes, webcams have lower resolution, smaller CCD'd and worse noise artifacts, but if I break them it will not be the end of the world.

 

So which webcam is good for this purpose?

Amazingly enough, this is a much harder question than it should be.  One thing I found out is how much manufacturers lie about their cameras. For example, I bought a "HD webcam" that supposadly can do 1080p. Turns out it is 640x480 RAW, and just enlarges the image it sends to you to 1080. Completely useless! It seems that almost all webcams can't actually do the resolutions they say they can. Some of them hint at this, when they say for example " 5 megapixel (effective resolution)".  That is usually weasel words for "We enlarge it to this size, even if it all looks like a bunch of lego blocks". So completely ignore this, we need to find another way of judging.

Things I intend to look for in a camera:

The above is ideal, in reality some cameras will match some features, others won't.  This is what I've found so far:

 

Camera Model
Info Link Price (qty1) Features Max
Resolution
(HxV)
Notes

Videologyinc 20K13XUSB USB Monochome CCD Camera

OEM
£100.00
  • CCD Sensor
  • Monochome (No bayer)
  • Standard Interface (USB2)
  • RAW Support
  • Linux support
  • Near-IR support (no filter)
752 x 582

The best option so far, unfortunately not "Cheap and readily available".
£100 is the top end of how much I'd be willing to spend for a CCD,
but the bigger problem is that it is almost impossible to get this camera.
The Manufacturer is an OEM, and will let you be a reseller if you're
willing to buy 1000 at once. I don't have £100,000, even if I could sell them all.

Oh, and I've not found a reseller which actually sells these bare, but I
suspect many of these find themselves in security cameras, etc...

Logitech C600 2MP HD Webcam

 Logitech Website £40.00
  • Standard interface (USB)
  • RAW Support
  • Linux support
  • Cheap and readily available
 1600×1200

How nice of Logitech, as well as usual
"8 megapixel" resolution stuff, they also
provide the native resolution, which is 2megapixels.

CMOS sensor, and Bayer matrix, so
not perfect.

 Logitech C270 HD Webcam
 Logitech Website  £18.00  
  • Standard interface (USB)
  • RAW Support
  • Linux support
  • Cheap and readily available
1280x720 Cheap version of above, lower resolution, CMOS Sensor and Bayer matrix
           
           

 

 It seems that Logitech are the only consumer level camera maker that actually allow you to stream out the RAW Data (aka Bayer data). This means that rather than dealing with the interpolation, you get each pixel as it is, representing the bayer pattern. Not as good as pure monochrome, but better than the rest.

While they come with a IR filter, there is a lot of information online on how to remove it, so Logitech are probably the "least worst" option that is currently available. I'll give them a try.